I also have an identical problem, as ScottieG
I have an iphone 6 plus - O/S 8.1.3 and i cannot connect using a Lenovo G50-30 NOTEBOOK with O/S Windows 8.1
It worked fine until 2 or so weeks ago.
If i use the USB cable - i can no longer use personal hotspot, as a tethered mobile.
I have every update on both notebook, and phone. both are relatively new - christmas notebook, November iphone 6 plus.
I can connect easily using public wifi / using either pc or phone.
i can connect using pc wifi and setting iphone 6 plus as a wifi connection.
bluetooth has never worked with much success, so its not bothered me, however , as much as I've googled to solve the problem - it makes no difference.
Microsoft problem solvers (fixits) does not make any difference.
In desperation, i completely wiped the pc to return it to "zero" that way i could establish if it was a settings or other issue, caused by myself.
Made no difference.
I completely formatted and wiped the iphone 6 plus yesterday, for the same reason - again, made no difference.
I checked the USB cable, just in case, again, made no difference, made no difference, iphone is visible on system, just cannot connect using tether0GB ed method.
I contacted my network provider, to ask if the problem was their doing - they stated no, my contract is 20gb per month - and I'm not even close to using that.
so, anyone got any answers??